Threaded rod nut
Screw: surface cut with spiral groove cutting with a conical cylindrical or conical spiral groove. The screw has a different head, like the head of the picture is called the outer six angle screw. There are other, such as flat screw, inner six angle screw etc..
An element of a nut is the nut, bolt or screw rod together to play of the fastening parts, all production machinery manufacturing must be used according to the different materials, is divided into several major types of carbon steel, stainless steel, non-ferrous metals. The function is to tighten the bolt or screw together. A nut is a part which is tightly connected to the mechanical device, through the inner thread, the same specification nut and bolt can be connected together, for example, M4-P0.7 nut can only be connected with the M4-P0.7 series of bolts.